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Senior South Korean officials, who met with Secretary of State John Kerry in Seoul on Friday, said their government also was willing to resume humanitarian assistance to the North following weeks of escalating threats by North Korean leader Kim Jong Eun to attack American and allied targets in North Asia and the Pacific.

South Korean officials said the aid shipments could form a pillar of recently elected President Park Geun-hye's "trust" policy toward Pyongyang. Ms. Park seeks to reverse some of the hard-line tactics pursued by her predecessor, Lee Myung-bak.

However, Mr. Kerry during his visit also delivered a renewed warning, saying North Korea would be making a "huge mistake" by conducting new weapons tests, as it appears prepared to do. "We're going to continue to stand our ground," he told a business group in a speech in Seoul Friday, saying the U.S. doesn't bluff on security matters.

Mr. Kerry, who travels next to China, also said Beijing should "put some teeth" into its policy of a nuclear-free Korean peninsula.

Nonetheless, the aim of Mr. Kerry's trip to South Korea was to reduce tensions, and South Korea indicated it was willing to try. "The window for dialogue is always open," South Korean Foreign Minister Yun Byung-se said Friday following his meeting with Mr. Kerry. "We are always ready to provide humanitarian aid, in principle."

Mr. Kerry was visiting South Korea as part of a three-nation North Asia tour focused on defusing a standoff with North Korea. Pyongyang didn't respond Friday to the overture for talks.

The recent crisis began with Pyongyang's testing of nuclear weapons and long-range missiles starting late last year. The Obama administration responded by initiating new economic sanctions against North Korea and overseeing stepped-up military exercises with South Korea beginning last month.

U.S. and South Korean officials are concerned Mr. Kim is preparing to launch a midrange Musudan missile while Mr. Kerry is in the region. The top American diplomat visits China on Saturday and Japan on Sunday.

The Obama administration has been divided over the utility of diplomacy with North Korea since taking office in 2009.

ENLARGE

U.S. Secretary of State John Kerry, left, and South Korean Foreign Minister Yun Byung-Se give a joint press conference on Friday in Seoul.
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President Barack Obama has pledged to engage with some of Washington's staunchest enemies, including Iran, in a bid promote stability and contain the spread of nuclear weapons. But the White House believes it has been rebuffed in its earlier diplomatic overtures toward the North.

Just weeks after Mr. Obama took office, North Korea conducted its second nuclear weapons test. Last year, Mr. Kim scrapped an agreement with Washington that allowed for the provision of food assistance by launching a long-range rocket in violation of United Nations Security Council resolutions.

Mr. Kerry said in Seoul that the U.S. wouldn't attempt to block any efforts by Ms. Park to resume a dialogue with Mr. Kim. And the U.S. secretary of state said Washington would consider resuming its own diplomatic channel should Pyongyang display a willingness to begin dismantling its nuclear-weapons program.

ENLARGE

Mr. Kerry noted that Mr. Obama recently called off some additional U.S.-South Korean military exercises in an effort to lower tensions between Washington and Pyongyang.

"We would never stand in the way…of a sovereign country to decide to talk bilaterally," Mr. Kerry said. "We also said that we'd engage in bilateral talks in the right circumstances."

The former U.S. senator, however, expressed skepticism that the North could be trusted in negotiations. He said the U.S. was unlikely to resume its own humanitarian assistance to the North because of Kim Jong Eun's backing out of last year's aid agreement.

"We've been down that path before, and we've disappointed by the breach of those agreements," Mr. Kerry said.

Rising Tensions on the Korean Peninsula

Threats by North Korea against its southern neighbor have escalated, deteriorating fragile relations between Pyongyang and Seoul. The threats are an annual occurrence during U.S. military exercises in South Korea but have been particularly vociferous this year.

Leaving North Korea

South Korean vehicles carrying products used and produced by South Korean companies in North Korea's Kaesong Industrial Complex arrived at a border crossing in Paju, north of Seoul, on Wednesday. Reuters

Mr. Kerry and Mr. Yun also discussed the potentially thorny issue of a civilian nuclear cooperation agreement that Washington and Seoul are seeking to conclude before Ms. Park visits the White House last week.

The agreement allows for the U.S. to share American-origin nuclear fuel and technology with South Korea. But Seoul's negotiators are seeking to gain U.S. approval to allow South Korea to begin producing its own nuclear fuel, through both the enrichment of uranium and the reprocessing of spent reactor fuel. U.S. officials are wary of agreeing to such terms, as such technologies could also give Seoul the ability to develop weapons-grade nuclear fuel.

Both diplomats said they were optimistic that a compromise agreement could be reached. But neither official would outline the likely terms for the deal.

Mr. Kerry will travel to Beijing on Saturday. He said he would press Chinese officials to more aggressively seek to stop Kim Jong Eun from threatening the South and advancing North Korea's nuclear program. Beijing is by far North Korea's largest trade partner and its only remaining strategic ally in Asia.

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